Metro Working on New Plan To Fix Leaking Red Line Tunnel

Metro Working on New Plan To Fix Leaking Red Line Tunnel

Leaks in the problem-plagued tunnel stretching from Bethesda to D.C. led to Friday's frustrating commute

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Metro General Manager Paul Wiedefeld discusses the Red Line and other Metro issues during a meeting with the Montgomery County Council Tuesday

Andrew Metcalf

The arcing insulator incidents that snarled Friday’s rush hour commute on Metrorail from Bethesda to Dupont Circle were caused by the transit system’s familiar foe—water leaking into the Red Line tunnel.

On Tuesday, General Manager Paul Wiedefeld said Metro is working on finding a permanent fix for the leaking underground tunnel, but doesn’t have a plan or a timeline for when the problem will be fixed. The leaky tunnel stretches from the Medical Center station in Bethesda to Farragut North in Washington, D.C.

Wiedefeld spoke about the problem caused by arcing insulators, which produce smoke when debris or other matter comes in contact with the electrified third rail, during a briefing with the Montgomery County Council in Rockville.

He said Metro crews pump hundreds of thousands of gallons of water daily out of the tunnel, which sits below the water table. The tunnel was built without a waterproof membrane through rock underneath Rock Creek. The rock has joints and fractures and the concrete tunnel is porous, allowing groundwater to seep onto the tracks. The issue is particularly problematic at the Medical Center station in Bethesda because it was built through clay-rich rock known as saprolite that’s more permeable than the bedrock that surrounds the other stations along the tunnel segment.

As the water pools below the tracks, it mixes with debris and turns into a mucky substance that is kicked up by passing trains, causing some of the muck to land on the electrified third rail, which creates a “spark like a sparkler,” Wiedefeld explained. When this occurs, Metro closes the track to fix the issue—sometimes causing significant delays such as those that occurred during Friday’s commute.

Water in the tunnel has in the past corroded the rail and other equipment in the tunnel according to a slide from this 2014 Metro presentation.

No other tunnel in the system is porous, according to Wiedefeld, and the arcing incidents typically happen during the spring or early summer after heavy rainfalls.

Wiedefeld said one idea to fix the leaking problem would be to install a new, waterproof tunnel inside the current tunnel. But he also said Metro engineers are looking at new technology that could be less expensive that “has shown promise in other properties around the country.” Wiedefeld would not detail that technology because Metro is trying to negotiate a deal for it to be used in the tunnel.

The leaking has been occurring for more than two decades. In April 2016, Metro indefinitely postponed a plan to close the Bethesda, Medical Center and Grosvenor-Strathmore stations for 14 weekends to install a new drainage system and a waterproof precast concrete arch in the tunnel after Wiedefeld said the one bid on the estimated $12.2 million project came in “significantly higher” than Metro estimated.

He said the new technology that Metro is considering could be piloted “in the very near future.” It could prevent the moisture from seeping through the tunnel’s walls and possibly prevent Metro from having to build a tunnel inside a tunnel, according to Wiedefeld.

Council President Roger Berliner, who has toured the tunnel, said it resembles Luray Caverns with visible mineral deposits and water dripping down.

“You see water coming in and you say, ‘oh my goodness’ this can not work very well for our future,” Berliner said.

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